NASA halted fueling of the shuttle Saturday morning after detecting the leak, associated with the gaseous hydrogen venting system outside the shuttle's external fuel tank, NASA said. The system is used to carry excess hydrogen safely away from the launch pad.

Shuttle managers will assess the leak and meet at 2 p.m. ET Sunday to discuss what steps to take next, including setting a new launch date, NASA said. They planned a news conference after the meeting, the space agency said.

The earliest the shuttle could be ready to launch now is Wednesday, NASA said, but there is a conflict on that date with the scheduled launch of the Lunar Reconnaissance Orbiter/Lunar Crater Observation and Sensing Satellite.